Datatype of PRIMARY KEY

Question

Namaskar,
i just read a question in an Interview..it asked..
What is the Datatype of PRIMARY KEY Oracle Internally uses?
1.Binary Integer
2.Varchar2
3.Number
is it Binary integer?
Thanks in Advance!!!

Answer 1

select owner, DATA_TYPE, count(*)
from dba_constraints join dba_cons_columns
using (owner,table_name,constraint_name)
join dba_tab_columns
using (owner,table_name,column_name)
where constraint_type='P'
group by owner,data_type
order by 1,2;
OWNER      DATA_TYPE         COUNT(*)
DBSNMP     DATE                     2
DBSNMP     NUMBER                   1
DBSNMP     RAW                      9
DBSNMP     VARCHAR2                 2
EXFSYS     NUMBER                   2
EXFSYS     VARCHAR2                22
RMAN       NUMBER                  31
SCOTT      NUMBER                   2
SYS        CHAR                     2
SYS        DATE                     3
SYS        NUMBER                 523
SYS        RAW                     34
SYS        TIMESTAMP(3)             1
SYS        TIMESTAMP(6)            12
SYS        TIMESTAMP(9)             1
SYS        VARCHAR2                92
SYSTEM     NUMBER                 172
SYSTEM     RAW                      8
SYSTEM     ROWID                    1
SYSTEM     VARCHAR2                70as you can see, oracle uses lots of different data types as primary key